fn main() {
    bool a = !true
    bool b = a
    var b1 =!a
    print(a, b, b1, '\n') // falsefalsetrue

    var str = 'hello world'
    bool c = !(str.len() > 0)

    string str2 = ''
    bool d = !(str2.len() == 0)
    print(c, d, '\n') // falsefalse

    bool e = (1 + 1) != 0
    bool f = !(3.1415926 != 0.0)
    print(e, f, '\n') // truefalse

    var sum = fn(int a, int b):int {
        return a + b
    }

    var g = sum(12, -1) catch err {
        println('no err')
        0
    }

    bool has_err = false
    bool h = has_err
    bool i = !has_err
    print(g, h, i, '\n') // 11falsetrue
}